Nanoparticle Catalysts Research Articles

Kinetic research and optimized particle size for high-performance of CdS NP photocatalyst.

Metal semiconductors are important materials for photocatalytic technology, and their morphology and size have the great influence on photocatalytic performance. Therefore, the detailed exploration of the size effect is significant for the photocatalytic reaction. Herein, CdS nanoparticles (NPs) with different particle sizes were prepared for photodegradation of methylene blue, and the effects of particle size on photodegradation were studied using CdS NPs as a catalyst. The rate-determining step of photodegradation is determined theoretically by deriving the kinetic order of the photodegradation reaction, and the relationships of size and performance are explored. The results show that the particle size of the CdS NP catalyst has an obvious influence on the photodegradation rate and the rate constant, and the size effects show a "volcano" trend, implying that the catalyst activity is best when the particle size of the catalyst is moderate. The size influences on the adsorption/desorption, light utilization, and carrier efficiency of the catalyst originate from the influence of size on the surface properties and energy band. This study provides a new understanding on the effect of catalyst size on its properties, and this finding of optimum sizes of catalyst possessing better activity is valuable, which has a significant guidance for developing high-performance catalytic materials.

3D Printing of Graphene Aerogel Microspheres to Architect High-Performance Electrodes for Hydrogen Evolution Reaction.

The hydrogen evolution reaction (HER) efficiency is highly dependent on the electrocatalysts microstructure and the macrostructure of the electrodes. Herein, the graphene aerogel microspheres loaded with well-dispersed ultrafine Ni/Co nanoparticles catalyst is prepared through electro-spraying, in-situ crosslinking, freeze-drying, and pyrolysis, and then is utilized to print the HER electrode via direct ink writing (DIW). The obtained graphene-based aerogel microspheres possess peculiar cabbage-like mesoporous structures which allow ready access of reaction species to active sites, optimal mass transfer, and proton diffusion within the microspheres. DIW 3D printing achieves the ordered control on the periodic lattice macro-geometry and thus facilitates the fast gas bubble evolution and release from the electrode surface. The as-fabricated 3D electrode possesses a low overpotential of 341 mV at 10 mA cm-2, a decrease by 31.5% compared to 3D printed electrode directly from 2D graphene, and a low Tafel slope of 119.1 mV dec-1, 40% lower than that of the electrodes fabricated via directly casting the aerogel microspheres. Furthermore, the 3D-printed electrode of aerogel microspheres displays good HER stability. This work provides a good approach for constructing high-performance HER electrodes through 3D printing of graphene aerogel microspheres.

The Impact of Metal-Support Interaction on the Structure and Activity of Carbon-Supported Ni Nanoparticle Catalysts for Alkaline Hydrogen Oxidation Reaction.

The effect of the carbon support─Ketjenblack (CKB) and Vulcan (CV)─on the Ni/C catalyst properties toward alkaline hydrogen oxidation reaction (HOR) was investigated. Both Ni/CKB and Ni/CV presented improved catalytic activity with an increase in Ni particle size; however, Ni/CKB showed activity significantly higher than that of Ni/CV at the same particle size. The reason for the difference in the HOR activity due to the types of carbon support was revealed to be the difference in the 3D structure of Ni nanoparticles determined by metal-support interaction, which is changed by the surface structures of carbon supports. These findings bring light to the critical importance of the metal-support interaction in the development of the HOR catalysts.

Application of Laser‐Generated Au‐Ag/Al2O3 Nanoparticle Catalysts for the Selective Catalytic Oxidation of 5‐(Hydroxymethyl) Furfural to 2,5‐Furan‐Dicarboxylic Acid

AbstractConversion of lignocellulosic biomass‐derived 5‐(Hydroxymethyl) furfural (HMF) into 2,5‐Furandicarboxylic acid (FDCA) has a high potential to replace petroleum‐based feedstocks for the production of plastics. In this study, a green synthesis strategy for the selective oxidation of HMF to FDCA is reported by using laser‐generated and specifically designed bimetallic AuAg nanoparticle catalysts supported on Al2O3 using molecular oxygen as oxidant and water as a solvent. Although supported AuAg catalysts are already known as suitable catalysts for this reaction, the optimal reaction conditions (type of base, reaction temperature, oxygen pressure), Au : Ag composition, role of metal‐support effects and origin of the active site still remain under debate. Interestingly, an Au9Ag1/Al2O3 catalyst exhibited the highest activity with a FDCA yield of up to 66 % at 80 % HMF conversion. Hereby, NaHCO3 (instead of NaOH) as a smoother base in 2 : 1 base:HMF ratio, low oxygen pressures of 5 bar, and a mild temperature of 150 °C were found optimal. The yield remained fairly stable on reuse of the catalyst for 3 cycles without hints of catalyst sintering or leaching. The titration of surficial hydroxyls on the AuxAgy/Al2O3 surface showed the highest density of acidic hydroxyls for the most active Au9Ag1/Al2O3 catalyst. The respective hydroxyls potentially originate from metal‐support interactions between the AuAg nanoparticles with the alumina support and act as Lewis acidic sites that oxidize the alcohol moiety of HMF to form FDCA with high selectively. In summary, this study shows that the catalytic activity of AuAg catalysts in HMF oxidation is not just linked to an alloying effect but also to a metal‐support effect where the AuAg nanoparticles appear to directly affect the local acidity of the support.

Sustainable Aerobic Transamidation and Esterification of N-Heteroaryl Amides by Heterogeneous Copper Catalyst

Transamidation of secondary amides via heterogeneous strategy has remained an unsolved problem. Here we report a novel and efficient approach for transamidation and esterification of ubiquitous N-heteroaryl amides with various amines and alcohols that exploits an engineered heterogeneous supported copper nanoparticles catalyst. This method overcomes the difficulty of heterogeneous catalysts, which can only achieve transamidation of primary amide driven by the emission of ammonia gas. A broad diversity of N-heteroaryl amides containing quinolin-2-yl, isoquinolin-1-yl, pyrazin-2-yl and pyridin-2-yl directing groups convert into corresponding α-ketoamides and α-ketoesters using needle-shape copper nanoparticles supported on γ-Al2O3 as heterogeneous catalyst. This environmentally benign, catalyst recyclable and easy-to-handle catalysis methodology will have great application prospects in the pharmaceutical synthesis and biological or chemical industry.

The Catalysts-Based Synthetic Approaches to Quinolines: A Review.

The most common heterocyclic aromatic molecule with potential uses in industry and medicine is quinoline. Its chemical formula is C9H7N, and it has a distinctive double-ring structure with a pyridine moiety fused with a benzene ring. Various synthetic approaches synthesize quinoline derivatives. These approaches include solvent-free synthetic approach, mechanochemistry, ultrasonic, photolytic synthetic approach, and microwave and catalytic synthetic approaches. One of the important synthetic approaches is a catalyst-based synthetic approach in which different catalysts are used such as silver-based catalysts, titanium-based nanoparticle catalysts, new iridium catalysts, barium-based catalysts, iron-based catalysts, gold-based catalysts, nickel-based catalyst, some metal-based photocatalyst, α-amylase biocatalyst, by using multifunctional metal-organic framework-metal nanoparticle tandem catalyst etc. In the present study, we summarized different catalyst-promoted reactions that have been reported for the synthesis of quinoline. Hopefully, the study will be helpful for the researchers.

Hydrotalcite-derived well-dispersed and thermally stable cobalt nanoparticle catalyst for ammonia decomposition

Ammonia is a carbon-free hydrogen carrier, and development of non-noble metal catalyst to decompose ammonia into hydrogen is desirable for practical applications. However, the metal catalyst is challenged by the sintering of metal particles under high-temperature reaction conditions. In this study, a series of Li-, Al-, and Co-containing hydrotalcite-like compounds (HTlc) were synthesized by co-precipitation and used as precursors to prepare well-dispersed and thermally stable Co nanoparticle catalysts for ammonia decomposition. The obtained precursors and catalysts were characterized by means of X-ray powder diffraction (XRD), temperature-programmed reduction (H2-TPR), X-ray photoelectron spectroscopy (XPS), high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM), and so on. All of the precursors formed hydrotalcite-like phase, which consisted of Li–Al–(Co) HTlc and/or Co–Al HTlc dependent on the Co content. Upon calcination at 500 °C, HTlc decomposed into an Al-substituted Co3O4 spinel oxide, as confirmed by two distinctly separated reduction steps in H2-TPR. Following reduction at 700 °C, well-dispersed Co metal nanoparticles with an average particle size of ∼9.2–12.4 nm were obtained. It was suggested that the incorporation of Al3+ into Co3O4 led to a strong interaction between cobalt and aluminum, which suppressed the crystal growth of Co3O4 and the sintering of Co metal during the thermal treatments, resulting in good Co dispersion. The optimal LiAlCo(1.5) catalyst showed superior activity than that prepared by impregnation method, giving almost complete conversion of ammonia at 575 °C under a space velocity of 5,000 mL gcat–1 h–1. More importantly, this catalyst maintained stable activity at 625 °C for 100 h, exhibiting high stability and sintering resistance. The good catalytic performance was attributed to the high Co metal dispersion and strong metal–support interaction benefiting from the uniform distribution of cobalt in the HTlc precursor. These results demonstrate the applicability of HTlc to the preparation of metal catalysts with improved dispersion and thermal stability.

Development of a Niobium-Based Coordination Compound with Catalytic Applications for Green Hydrogen Evolution

Green hydrogen (H2) offers a sustainable alternative to non-renewable energy sources. This study focuses on enhancing H2 generation from sodium borohydride (NaBH4) using a platinum nanoparticle (Pt-NP) catalyst supported on a niobium-based coordination compound, [Nb(BDC)0.9(PDC)0.1]n, synthesized via a solvothermal method with 1,4-benzenedicarboxylic acid (BDC) and 2,5-pyridinedicarboxylic acid (PDC). Characterization techniques including Scanning Electron Microscopy (SEM), Energy Dispersive X-ray Spectroscopy (EDS), Brunauer–Emmett–Teller (BET) analysis, Raman spectroscopy, and X-ray diffraction (XRD) confirm the morphology, composition, surface area (398.583 m2g−1), and crystallinity of the material. The in situ synthesized Pt-NPs showed a hydrogen generation rate (HGR) of 86.588 mL min−1 g−1 when alone, while the supported catalyst achieved an enhanced HGR of 119.020 mL min−1 g−1 under optimal conditions (10 mmol% Pt, 0.5 mmol NaBH4, 303.15 K). The low activation energy (Ea) of 16.38 kJ mol−1 indicates efficient catalysis. The catalyst maintained stable performance in recycling tests, demonstrating its potential for practical applications in H2 evolution from NaBH4.

Emerging Carbon-Based Catalysts for the Oxygen Reduction Reaction: Insights into Mechanisms and Applications

The oxygen reduction reaction (ORR), as a key electrode process in fuel cells and metal-air batteries, plays a pivotal role in advancing clean energy technologies. However, the slow kinetics and high overpotential of the ORR significantly limit the efficiency of these energy devices. Therefore, the development of efficient, stable, and cost-effective ORR catalysts has become a central focus of current research. Carbon-based catalysts, with their excellent conductivity, chemical stability, and tunable structural features, have emerged as promising alternatives to traditional precious metal catalysts. Nevertheless, challenges remain in the design of active sites, the tuning of electronic structures, and the large-scale synthesis of carbon-based catalysts. This review systematically introduces the fundamental mechanisms and key factors influencing the ORR, providing an analysis of the critical variables that affect catalyst performance. Furthermore, it summarizes several common methods for synthesizing carbon-based catalysts, including pyrolysis, deposition, and ball milling. Following this, the review categorizes and discusses the latest advancements in metal-free carbon-based catalysts, single-atom and dual-atom catalysts, as well as metal-based nanoparticle catalysts, with a particular focus on their mechanisms for enhancing the ORR performance. Finally, the current state of research on carbon-based ORR catalysts is summarized, and future development directions are proposed, emphasizing the optimization of active sites, improvements in catalyst stability, and potential strategies for large-scale applications.

Multiscale simulations for the study of adsorption of dibenzothiophene on molybdenum disulfide nanoparticle catalysts

Multiscale simulations for the study of adsorption of dibenzothiophene on molybdenum disulfide nanoparticle catalysts

Construction of Porous Organic Polymer Coordinated Palladium Nanoparticle Catalysts for Catalytic Synthesis of Coumarin Derivatives

Construction of Porous Organic Polymer Coordinated Palladium Nanoparticle Catalysts for Catalytic Synthesis of Coumarin Derivatives

DNA Duplex Containing Ag+-Mediated Cytosine-Cytosine Base Pairs as a Catalyst Precursor for the 4-Nitrophenol Reduction with NaBH4.

Catalytic applications of DNA duplexes containing Ag+-mediated cytosine-cytosine base pairs (C-Ag+-C) have not been well investigated. In this study, we demonstrate a novel approach for forming highly active DNA-capped Ag nanoparticle (DNA-AgNP) catalysts for the reduction of 4-nitrophenol (4-NP) using sodium borohydride (NaBH4). This approach is based on the in situ generation of DNA-AgNPs from DNA duplexes containing C-Ag+-C (DNA duplex-Ag+). UV-vis spectroscopic analysis suggests that the DNA duplex-Ag+ complex acts as an excellent catalyst precursor for 4-NP reduction with NaBH4. Transmission electron microscopy observations of the reaction solution after the 4-NP reduction reaction using DNA duplex-Ag+ provided detailed experimental insights into the mechanism of the catalytic activity of DNA duplex-Ag+ for 4-NP reduction. In the reaction solution, DNA-AgNPs were initially formed (DNA duplex-Ag+ + NaBH4 → DNA-AgNPs) and then served as water-soluble catalysts for 4-NP reduction. Notably, the catalytic properties of the DNA-AgNPs generated in situ were affected by the DNA strand length and sequence. The properties of DNA duplex-Ag+ may provide a new application of DNA molecules containing metallobase pairs as water-soluble catalyst precursors.

Turning on Low-Temperature Catalytic Conversion of Biomass Derivatives through Teaming Pd1 and Mo1 Single-Atom Sites.

On-purpose atomic scale design of catalytic sites, specifically active and selective at low temperature for a target reaction, is a key challenge. Here, we report teamed Pd1 and Mo1 single-atom sites that exhibit high activity and selectivity for anisole hydrodeoxygenation to benzene at low temperatures, 100-150 °C, where a Pd metal nanoparticle catalyst or a MoO3 nanoparticle catalyst is individually inactive. The catalysts built from Pd1 or Mo1 single-atom sites alone are much less effective, although the catalyst with Pd1 sites shows some activity but low selectivity. Similarly, less dispersed nanoparticle catalysts are much less effective. Computational studies show that the Pd1 and Mo1 single-atom sites activate H2 and anisole, respectively, and their combination triggers the hydrodeoxygenation of anisole in this low-temperature range. The Co3O4 support is inactive for anisole hydrodeoxygenation by itself but participates in the chemistry by transferring H atoms from Pd1 to the Mo1 site. This finding opens an avenue for designing catalysts active for a target reaction channel such as conversion of biomass derivatives at a low temperature where neither metal nor oxide nanoparticles are.

Reactivity and Stability of Reduced Ir-Weight TiO2-Supported Oxygen Evolution Catalysts for Proton Exchange Membrane (PEM) Water Electrolyzer Anodes.

Reducing the iridium demand in Proton Exchange Membrane Water Electrolyzers (PEM WE) is a critical priority for the green hydrogen industry. This study reports the discovery of a TiO2-supported Ir@IrO(OH)x core-shell nanoparticle catalyst with reduced Ir content, which exhibits superior catalytic performance for the electrochemical oxygen evolution reaction (OER) compared to a commercial reference. The TiO2-supported Ir@IrO(OH)x core-shell nanoparticle configuration significantly enhances the OER Ir mass activity from 8 to approximately 150 A gIr-1 at 1.53 VRHE while reducing the iridium packing density from 1.6 to below 0.77 gIr cm-3. These advancements allow for viable anode layer thicknesses with lower Ir loading, reducing iridium utilization at 70% LHV from 0.42 to 0.075 gIr kW-1 compared to commercial IrO2/TiO2. The identification of the Ir@IrO(OH)x/TiO2 OER catalyst resulted from extensive HAADF-EDX microscopic analysis, operando XAS, and online ICP-MS analysis of 30-80 wt % Ir/TiO2 materials. These analyses established correlations among Ir weight loading, electrode electrical conductivity, electrochemical stability, and Ir mass-based OER activity. The activated Ir@IrO(OH)x/TiO2 catalyst-support system demonstrated an exceptionally stable morphology of supported core-shell particles, suggesting strong catalyst-support interactions (CSIs) between nanoparticles and crystalline oxide facets. Operando XAS analysis revealed the reversible evolution of significantly contracted Ir-O bond motifs with enhanced covalent character, conducive to the formation of catalytically active electrophilic OI- ligand species. These findings indicate that atomic Ir surface dissolution generates Ir lattice vacancies, facilitating the emergence of electrophilic OI- species under OER conditions, while CSIs promote the reversible contraction of Ir-O distances, reforming electrophilic OI- and enhancing both catalytic activity and stability.

Hollow silicalite-1 encapsulated nickel nanoparticles as highly stable catalysts in maleic anhydride hydrogenation

Anchoring active metal particles in zeolite cages can significantly improve catalytic stability. In this study, hollow silicalite-1 (HoS-1) encapsulated Ni nanoparticles catalyst (Ni@HoS-1) was prepared using the impregnation method and applied in MA hydrogenation. The encapsulation mechanism was explained as the zeolite wall restricting the evaporation of water in HoS-1, hence Ni particles would be spontaneously enriched within the zeolite cage after drying and calcination. Experiments revealed the specially designed structure effectively protected Ni particles from leaching, and after 5 cycles in liquid-phase batch reactions, the final MA conversion of Ni@HoS-1 is 40.8 % higher than that of Ni/S-1 (85.5 % vs 44.7 %). Moreover, the low acidity of Ni@HoS-1 also delayed the accumulation of carbon deposits, extending the continuous reaction lifespan from 128 h of Ni/S-1 to 188 h. These findings provided a new perspective for the controllable locating of active metal sites against the supports.

Investigation on CuO nanoparticle enhanced mahua biodiesel/diesel fuelled CI engine combustion for improved performance and emission abetted by response surface methodology

In this study, the characteristics of diesel engines were tested with in-house produced mahua biodiesel blended with diesel and copper oxide nanoparticles (CuO NP) catalyst. The preliminary investigation used mahua biodiesel-diesel blends (M10, M20, and M30) among them M20 outperformed. Further M20 and CuO NP with concentrations of 25, 50, and 75 ppm are studied. Finally, the response surface methodology (RSM) was used to determine the appropriate NP concentration for M20. The findings showed that the blend of M20 with 60 ppm NP at 80% load had the highest desirability (0.9740), and the developed RSM model predicted engine responses with a mean absolute percentage error (MAPE) of 3.0962% to the confirmation test confirming the model’s accuracy. The optimized M20NP60 blend demonstrated superior combustion, performance and emission characteristics.

Trace Iron-Modified CeO₂-Supported Core-Shell CoO@Co Catalyst for Selective Conversion of Furfural to 1,5-Pentanediol.

In the conversion of furfural using non-noble metal catalysts, preferential cleavage of the C2-O bond followed by hydrogenation of the C=C bond facilitates selective access to valuable 1,5-pentanediol (1,5-PeD). Herein, we developed CeO₂ loaded core-shell CoO@Co nanoparticle catalysts. Adjusting Co loading, Fe doping, and reduction temperature improved reaction efficiency. 7Co-0.2Fe/CeO₂ catalysts reduced at 500 °C demonstrated optimal performance. 1,5-PeD produced at 54.76 mmol/gCo/h, representing the top activity levels among the reported catalysts. H₂-TPR, XRD, HAADF-STEM, FT-IR, XPS, and XANES were employed to investigate the catalyst structure-activity relationship. Co2+ cleaves furan ring C-O bond, Co⁰ promotes double-bond hydrogenation. The CoO@Co structure favors the desired 1,5-PeD production route. Trace Fe species optimize the Co2+/Co⁰ ratio, enhance the substrate adsorption, and inhibit the furan ring saturation. These findings emphasize the importance of fine-tuning catalyst structure and composition for selectivity improvement.

Highly stable platinum catalyst encapsulated with mesoporous silica for preferential oxidation of CO in H2-rich stream

Preferential oxidation of CO in H₂-rich streams (PROX) is an effective method to reduce trace amounts of CO for proton exchange membrane fuel cells. However, developing highly stable catalysts for practical reaction conditions achieving the 50:50 goal—below 50 ppm CO concentration with 50% O₂ selectivity—remains challenging. Here, we report a highly stable Pt nanoparticle catalyst encapsulated in mesoporous silica (Pt@mSiO2) loaded on a monolith, which achieves the 50:50 goal. Over 1000 h of continuous PROX reactions in the presence of H2O and CO2, the catalyst maintained an average CO concentration of ca. 33 ppm and O2 selectivity of ca. 50%. The excellent activity, selectivity, and long-term stability of Pt@mSiO₂, which can be attributed to the small size (ca. 2.7 nm) of Pt nanoparticles stably encapsulated in interconnected micro- and meso-porous silica without agglomeration, offer great potential for practical PROX applications.

Catalytic reduction of p-nitrophenol and Eosin Yellow by lemongrass tea-stabilized copper nanoparticles

ABSTRACT Green synthesis of nanoparticles for catalytic applications remains of continued interest, especially for reactions that would occur on an industrial scale or that may be of environmental significance. Here, ultrasmall 2.1-nm copper nanoparticles were synthesized under ambient conditions using a copper sulfate pentahydrate precursor and lemongrass extract as a reducing and capping agent. Their potential to act as catalysts was tested using model reactions: the sodium borohydride reduction reactions of p-nitrophenol and Eosin Yellow. Kinetics measurements were obtained with visible time-course spectroscopy and showed that copper nanoparticles effectively catalyzed both reactions. Temperature dependence followed Arrhenius behavior, indicating the catalyst surface was accessible to reactants. Activation energies of 59.2 and 38.5 kJ/mol were obtained for the reduction reactions of p-nitrophenol and Eosin Yellow, respectively. Large frequency factors for both reactions were found, implying large numbers of catalytic sites and/or facilitation of reaction by capping agents. This copper nanoparticle catalyst prepared via green synthesis demonstrates reproducible reduction behavior for two model reactions and observed rate constants that compare favorably with other copper nanoparticle catalysts, particularly in terms of rate constants normalized for available surface area and including catalysts produced via traditional synthetic methods.

Role of Interfacial Hydrogen in Ethylene Hydrogenation on Graphite-Supported Ag, Au, and Cu Catalysts.

A combined surface science/microreactor approach was applied to examine interface effects in ethylene hydrogenation on carbon-supported Ag, Au, and Cu nanoparticle catalysts. Turnover frequencies (TOFs) were substantially higher for supported catalysts than for (unsupported) polycrystalline metal foils, especially for Ag. Spark ablation of the corresponding metals on highly oriented pyrolytic graphite (HOPG) and carbon-coated grids yielded nanoparticles of around 3 nm size that were well-suited for characterization by X-ray photoelectron spectroscopy (XPS), high-resolution (scanning) transmission electron microscopy (HRTEM/STEM), and energy dispersive X-ray spectroscopy (EDX). Polycrystalline metal foils characterized by scanning electron microscopy (SEM), EDX, electron backscatter diffraction (EBSD), XPS, and low-energy ion scattering (LEIS) served as unsupported references. Employing a UHV-compatible flow microreactor and gas chromatography (GC) allowed us to determine the catalytic performance of the model catalysts in ethylene hydrogenation up to 200 °C under atmospheric pressure. Compared to the pure metal foils, the HOPG-supported metal nanoparticles exhibited not only strongly increased activity but also higher stability (slower deactivation) and differing reaction orders. For the most active Ag catalysts, DFT calculations were carried out to determine the adsorption energies of the reacting species on single-crystal surfaces as well as on carbon-supported and unsupported Ag nanoparticles. Adsorption of molecular hydrogen was very weak on all unsupported Ag surfaces, resulting in hydrocarbon-"poisoned" surfaces. However, when a carbon support was present, the adsorption strength of H2 on Ag nanoparticles increased on average by -0.5 eV, driven by changes in Ag-Ag distances near the metal-carbon three-phase boundary (whereas subsurface carbon lowers hydrogen bonding). On Cu particles, the interface effect was calculated to be somewhat weaker than for Ag particles. H2/D2 scrambling experiments on Ag catalysts then corroborated a facilitated hydrogen activation for carbon-supported metals. Thus, the carbon support effect is attributed to an improved hydrogen availability at the metal-carbon interface, controlling performance.